1. Field of the Invention
The present invention relates generally to a high specific speed centrifugal oxygenator for mixing a gas into a liquid.
2. Description of the Related Art
Centrifugal oxygenators have been developed for mixing a gas, such as oxygen, into a liquid, such as liquid waste, for absorption of the oxygen by the waste. One type of centrifugal oxygenator includes a venturi type inlet for air or oxygen which encircles a waste water inlet in a collector to aspirate air or oxygen directly into the wase water as it enters the collector. A recessed vortex type impeller is provided which is mismatched with its casing or collector; in other words having an oversized collector to provide a high agitation rate in the collector. The outlet of the collector is back-pressured by outlet nozzles to extend the duration of retention of the liquid and air mixture in the collector as well as increase the pressure therein. Continuous absorption of oxygen is thereby provided under high agitation and pressure with an extended mixing and retention time.
To increase the capacity of the existing centrifugal oxygenators, several units are run in parallel. However, it is more economical to utilize a single, larger unit instead of a plurality of smaller units in parallel. After testing, it has become apparent that the specific speed range of the known units cannot be used efficiently. If the flow rate is to increase and the nozzle pressure or head generated by the oxygenator is to remain constant, then a lower speed must be used. This is entirely possible, although lower speed units are larger and thus more expensive.